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Ind. Walnut Trees Not At Risk For Thousand Cankers Disease

A tree branch exhibiting the spots of dead tissue characteristic of Thousand Cankers Disease, a fungal infection that targets walnut trees.

Indiana Department of Natural Resources officials want Indiana residents to know that Thousand Cankers Disease is not killing black walnut trees in the Hoosier state.

DNR nursery inspector and compliance officer Vince Burkle says TCD, which is caused by mass attacks on black walnuts by infected beetles, is nothing to worry about for now.

“We do not have the disease actively killing trees, and insects actively attacking trees, in the state of Indiana,” Burkle says.

The fungus that causes TCD, Geosmithia morbida, is carried by walnut twig beetles. The beetles bore into black walnuts to feed on the tree’s tissues and pass the fungus under the bark, causing a canker.

One beetle can cause one canker, and it takes thousands of beetles to actually kill a tree, hence the name “Thousand Cankers Disease.”

Burkle says while the Forest Service has trapped walnut twig beetles from Indiana saw mills and evidence of the TCD fungus was found on a weevil in Yellowwood State Forest in 2014, the two instances were independent of each other and do not indicate a threat to Indiana black walnut trees.

TCD was originally found in New Mexico and has killed black walnut trees across western states, where conditions are dry and hot.

But in Midwestern states like Tennessee, researchers have seen trees recover after TCD outbreaks.

Burkle says that climate and precipitation could factor into this hardiness.

“Black walnut is not a plant that’s native to the western United States,” Burkle says, “so it’s growing in a totally different environment out there than it is out here.”

What does this mean for black walnut trees in the Midwest and the East?

Purdue associate professor of entomology, forestry and natural resources Matthew Ginzel says there’s hope.

“So, TCD is not a death sentence in the East. And we’re starting to understand what factors contribute to a tree’s ability to overcome that infection.”

Black walnut is Indiana’s most profitable timber crop.

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